This invention relates to thermal machines which convert thermal energy to either fluid energy or electrical energy, or pump heat by applying either fluid energy or electrical energy, without the intermediary conversion to shaft power, by employing oscillating positive displacement elements that subject a working fluid to a thermodynamic cycle.
In energy conversion, it is often necessary to convert heat energy to a more useful form, such as fluid energy or electrical energy, or to use fluid energy or electrical energy to pump heat to achieve a desired temperature. It is further desirable to convert energy at as high an efficiency as possible, limited only by the First and Second Laws of Thermodynamics. It is further desirable that this be done by machines that are simple, compact, quiet, reliable, and vibration-free and that are self-starting and self-regulating to load variations. The present invention meets these requirements and can be varied in configuration and function to match a wide range of output and performance requirements.
Broadly stated, the present invention relates to machines in which freely oscillating positive displacement mechanical elements periodically subject a working fluid to a thermodynamic cycle through continuous thermal energy interchange with the surroundings and thereby produce a net heating or cooling effect, a net work output or a combination of both without intermediary conversion to shaft work. The continuous thermal energy interchange (as opposed to the intermittent thermal energy interchange produced in spark or compression ignited combustion engines), caused by a temperature difference between a thermal source and sink, provides the driving potential through volume and pressure change (related by the equation of state of the working fluid), to produce the driving force for the self-excitation of the positive displacement elements. The self-exciting driving force is periodic and can be made as nearly sinusoidal as desired. The thermal oscillator's analog is an electrical oscillator (active parametric power oscillator) and as a result may be classed as an active parametric power oscillator that achieves conversion of thermal energy to mechanical energy by using a thermal potential (temperature difference) to parametrically pump, through periodic changes in the working fluid's pressure and volume, a mechanical oscillator to produce a periodic mechanical output. As a result, whenever a temperature difference is impressed on the thermal oscillator, thermal energy parametrically pumps a mechanical oscillator to produce periodic mechanical output and conversely, whenever a periodic mechanical input is impressed on the thermal oscillator, mechanical energy parametrically pumps thermal energy against a temperature difference. Coupling a thermal oscillator engine to a thermal oscillator heat pump (a thermodynamically reversed thermal engine) results in a thermally powered heat pump (refrigerator) with optional mechanical energy output. As a result of this electrical analog, a thermal oscillator may be defined as a mechanical parametric power oscillator having positive displacement elements (including linear-pistons, circular-vanes, epitrochoid rotors and combinations thereof) that is self-excited by an impressed temperature difference and converts thermal energy to mechanical energy, or by thermally reversing, pumps thermal energy by applied mechanical energy. Mechanical energy so utilized includes pressurized fluid or electrical power, which for shaft coupling (such as shaft output) requires a second machine (fluid pump/motor or electric generator/motor).
Thermal oscillators are classified as open or closed types. Open thermal oscillators are thermal oscillators that are periodically connected to an essentially constant temperature heat source and an essentially constant temperature heat sink by valving means that are driven and phased by the resonant oscillation of the positive displacement elements. Closed thermal oscillators are valveless thermal oscillators that periodically transfer the working fluid through heat exchangers in which the pressure at any time is approximately equal but periodically varies in phase with the working fluid's pressure throughout the oscillator.